Brian Cudahy has served as the director of the office of transit management with the Department of Transportation. He writes on Urban Architecture, focusing on the historical aspects of transit systems. In Under the Sidewalks of New York: The Story of the World's Greatest Subway System, he chronicled the development of the subway and provided a chronological overview of rapid transit. He has also written histories of the Boston subway, Hudson tubes, Pennsylvania railroad tunnels, and the Chicago rapid transit system.